Moderating panel discussions, I’ve found, tends to be either a challenge or a cakewalk. It’s tough when you’ve got a panelist who’s a blabbermouth, or one that’s shy. The audience is just as important as the people on stage: If they’re not fully engaged, it’s like there’s a gloomy little raincloud hovering over the room.

The panel I moderated on Monday at SXSW Interactive — “Lessons From Disruptors: Game-Changing Startups” — was the easy kind. The panelists were engaging and sometimes downright inspiring: Travis Bogard (Jawbone‘s VP of product and strategy), Matt Rogers (co-founder and VP of engineering at Nest) and Ren Ng (founder and CEO of Lytro). We also got a full house of folks who asked so many good questions that my work wasn’t really work. Mostly, I enjoyed listening to three smart tech entrepreneurs and made sure that we ended on time.

The three companies represented are quite different in some ways. Jawbone has been around for more than a decade, and has released multiple generations of its Bluetooth headset and expanded into new product categories. “Learning thermostat” maker Nest was started by veterans of the most disruptive big tech company of them all, Apple. Lytro sprung from Ng’s academic research on light-field photography and is his first startup.

Yet I was also struck by the things these businesses share. They all make hardware products — which makes them exceptions in Silicon Valley, which favors purely Web-based startups these days — and also design their own software and services. They all care about industrial design. They all compete with bigger companies that have been around for decades. And yes, they’ve all disrupted their industries.

The only downside of being on stage asking questions was that I couldn’t jot notes about the panel. Fortunately, members of the audience were busily sharing choice tidbits on Twitter. Here are some of the hour’s highlights in tweet form:

That last thought — “You can do it” — came from Lytro’s Ng. It was the one that concluded the panel, and nicely summed up things. Then again, so did the parting shot of Nest’s Rogers, who said that this stuff is a thousand times harder that you expect it’s going to be. It is really hard to shake up a tech-product category — but it’s possible. The fact that it keeps happening is one big reason why I love my job.